I would like to take some fruit seeds back to my home country when we eventually move back to plant in my garden there. I emailed the ministry of agriculture (in my country) and they informed me that any seeds I bring in would have to be in sealed packages and would have to have a phytosanitary certificate.

I am thinking of rambutan and mangosteen seeds in particular. Does anyone have any idea where I might find these seeds with the appropriate packaging and certification? Thanks in advance.

Mangosteen seeds germinate when removed from the fruit and die very quickly, its unlikely you'd get any germination from a non-fresh seed.

Rambutans grown from seed often produce inferior fruit-- it is usually propagated by grafting or budding.

So, if you were looking to grow these for fruit production, I'd think about importing a small tree instead.